The present invention relates to a power abnormality indicating circuit, and especially to circuit for indicating abnormality of a three-mode surge absorber of a public electric power. Other than indicating the abnormality of the L-N, L-G, N-G surge absorbing devices, the present invention can prevent current leakage as destroys occurs in above modes.
The general power receptacles for surge protection use metal oxide varistors or other transient/surge absorbers for suppressing surge wave. These elements will heat as absorbing surge wave, even a large surge wave will induce a short circuit. Therefore, temperature fuses or current fuses are used to prevent abnormality.
In general, the cutting-off of fuses is used to determine the abnormality of a surge protection indicator. However, in order to prevent that the leakage current to the ground is too large, in general, the indicator only displays the condition of the input ends of line-neutral mode while the conditions of line-ground mode and neutral-ground mode are not displayed.
Referring to FIG. 1, a prior art circuit for indicating abnormality of a surge absorber is illustrated, which includes two surge absorbing devices 10 and 30 and an abnormal indication circuit 20. The L-N end in the three-mode in public power supply is connected to the surge absorbing device 10 in series. The surge absorbing device 30 is serially connected between the L-G and N-G ends. The surge absorbing device 10 has a two-end temperature sensing fuse 101 capable of suffering from a temperature of 139xc2x0 C. and a metal oxide varistor 102. When the metal oxide varistor 102 has abnormality, it will heat gradually. Since it tightly resists against the two-end temperature sensing fuse 101, the metal oxide varistor 102 will heat and finally burn-cut the two-end temperature sensing fuse 101 so that the surge protection indicator D2 will extinguish due to no current flowing therethrough.
The surge absorbing device 30 has two metal oxide varistors 301 and 302 and a two-end temperature sensing fuse 303 capable of suffering from a temperature of 139xc2x0 C. When the metal oxide varistor 301 has abnormality, it will heat gradually. Since it tightly resists against the two-end temperature sensing fuse 303, the metal oxide varistor 301 will heat and finally burn-cut the two-end temperature sensing fuse 303, but the two-end temperature sensing fuse 101 does not burn-cut so that the surge protection indicator D2 will not extinguish. Namely, the fault of the surge absorbing device 30 of the L-G ends can not be detected. Furthermore, When the metal oxide varistor 302 has abnormality, it will heat gradually. Since it tightly resists against the two-end temperature sensing fuse 303, the metal oxide varistor 302 will heat and finally burn-cut the two-end temperature sensing fuse 303, but the two-end temperature sensing fuse 101 does not burn-cut so that the surge protection indicator D2 will not extinguish. Namely, the fault of the surge absorbing device 30 of the N-G ends can not be detected.
Accordingly, the primary object of the present invention is to provide a circuit for indicating abnormality of a three-mode surge absorber and a multiple-end fuse.
To achieve above objects, the present invention provides a circuit for indicating abnormality of a three-mode surge absorber of a public electric power serially connected to an input end and an output end of a public power supply, the circuit for indicating abnormality of a three-mode surge absorber of a public electric power comprising: a first two-end fuse having a first end coupled to the line input end; a first surge absorbing device coupled to a second end of the first two-end fuse and the neutral input end for absorbing a surge between the line input end and the neutral input end; a second surge absorbing device coupled to the line input end and the neutral input end for absorbing a surge between the neutral input end and ground input end; an abnormal indication circuit coupled to the first surge absorbing device, the second surge absorbing device and the neutral input end for indicating abnormalities in three-mode of a public power supply; and a second two-end fuse having a first end coupled to the second surge absorbing device, and a second end coupled to the ground input end for preventing abnormalities of parts. By the aforesaid circuit, other than indicating the abnormality of the L-N, L-G, N-G surge absorbing devices, the present invention can prevent current leakage as destroys occurs in above modes.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing.